Creak, creak, snap...

[karlt]

...In order to get lights and reflectors how I'd like, I decided to swap the racks between the MTB and road bike.

All goes well except one thing - one of the bolts in the frame at the drop-outs wouldn't come out. Eventually the head broke off - clearly seized in the hole with greater force than the structural strength of the bolt itself.

I'm guessing I'm going to have to drill out what remains. Aluminium frame. Someone tell me if I'm wrong.

[Brucey]

it does sound like you are going to have to do something like that.

But drilling steel bolts out of aluminium is tricky. especially if they are small.

I'd suggest some penetrant, a little heat, some tapping with a hammer. If you have a chum with a MIG welding set, have him add weld metal to the remains of the old bolt; the concentrated heat from the welding will break the bond of corrosion without trashing the finish on the frame if it is done carefully. I've removed many stubborn fasteners in this way.

If this doesn't work, you can still go with the drill.

cheers

[axel_knutt]

Drilling hard bolts out of a soft material doesn't work because the drill just wanders off centre and damages the workpiece. Even with the work held in a lathe or milling machine there is enough flex in the drill itself for it to damage the work.

I think your best bet might be a screw extractor, but even then it will be tall order if the screw is as small as M5.

[531colin]

I'm with Brucey...MIG or stick weld if there is any bolt sticking out.....put a blob of weld on it and try to turn the bolt with Mole grips.

Stud extractors (AKA easy outs....the last thing they are) are a pain in small bolts. You still have to drill the bolt. If you find an extractor small enough, its too thin and brittle, it snaps off in the bolt and you are worse off. They "grip" the bolt 'cos they are tapered, so they expand the bolt and its stuck more.

Ison Distribution used to sell left-hand drill bits for removing sheared bolts, but with a dropout you don't need this....just work from the wheel side of the dropout....drill say 3mm (start at 2mm?) as you hollow out the bolt* and the drill binds and torques the bolt, it MIGHT just come out.

*simultaneously heating and weakening the bolt

BTW, I think you fell foul of steel/alloy corrosion.....stainless bolts and copper grease are recommended, I think, somebody please say if I'm wrong!

[Graham O]

I'd be tempted to leave the remains of the bolt in place and drill another hole if you've got enough metal. Then just bend the rack frame a bit or make up an adapter. A bit of a bodge, but will be a lot easier than trying to remove the bolt.

[531colin]

I'd be tempted to leave the remains of the bolt in place and drill another hole if you've got enough metal. Then just bend the rack frame a bit or make up an adapter. A bit of a bodge, but will be a lot easier than trying to remove the bolt.

Or drill it all out and replace with 6mm bolt.....if there is enough metal!

[Graham O]

Or drill it all out and replace with 6mm bolt.....if there is enough metal!

I had thought of that, but presumably, you'd need a core drill to remove the bolt stub and surrounding metal. (Can you get core drills?) Whenever I've tried to drill a steel bolt out of alloy, I've always ended up with a nice hole next to the stub, which is still in place!

[reohn2]

I'd drill down the centre of the bolt starting with a 2mm bit,increasing slightly in diameter two maybe three increments, your last bit being the diameter of the size of the bolt's thread depth diameter ie; smallest diameter of the threaded part of the bolt.
This will leave a coil of thread left in the hole,I have been able in the past to get an end of this coil and unspring it from the threads of the hole.The heat and disturbance of drilling can help seperate "spring" from hole thread, as can thin oil such a plus gas,parafin or GT85.
Note:-Gently does it!
If you have enough room on the inside of the dropout,(there isn't usually enough room on the cassette side unless the hole is higher up on the d/out) and any removal method renders the thread usuable you can use a longer bolt and a nylock nut to secure the rack.
Note:-Gently does it!

[breakwellmz]

[quote="axel_knutt"]Drilling hard bolts out of a soft material doesn't work because the drill just wanders off centre and damages the workpiece. Even with the work held in a lathe or milling machine there is enough flex in the drill itself for it to damage..

This is why we have centre drills

http://www.ebay.co.uk/itm/DORMER-HIGH-S ... 4abd28cf40

[karlt]

Thanks chaps. Unfortunately it's the cassette side (law of sod, innit?).

I'm tempted to leave it be; I've got a spare P-Clip knocking around and may be able to adjust the rack legs (they're adjustable for different size wheels) to meet the holes from that mounted on the frame. Point about steel bolt in softer metal well taken.

[niggle]

Other things that can help:

1. Soaking overnight in a penetrating fluid like WD40 or even diesel.

2. Heating the alloy dropout immediately before applying any turning force to the sheared off bolt, e.g. by pouring boiling water on it, as alloy expands more than steel thus releasing its grip- this definitely helps as I have used it often to get bearings out of alloy castings.

3. Cutting a slot in any exposed bit of the sheared off bolt, e.g. with a Dremel tool, then using a screwdriver/screwdriver bit in a suitable tool, maybe an impact driver, but only if you can support the dropout enough to guarantee it won't be damaged by impact. Otherwise a screwdriver bit in a 3/8" square drive ratchet can give quite a lot extra turning leverage.

If you are going to try drilling through the bolt then centre punch the end of it if you can to help keep the drill bit centred, use new best quality drill bits, go slowly and start with a small one as 531collin said. I also agree with him about stud extractors, a nightmare in these circumstances.

For the future, again agreeing with 531collin, the main thing is to use copper grease on all types of steel fasteners screwed into alloy. Use either stainless or bright zinc plated (BZP) hi-tensile bolts. You could also consider using a long enough bolt to put a nylock nut on the other end, assuming there is enough room inboard of the dropout, (this might require some cutting to length).

If you do this the threads will be less exposed to the elements as well as giving you something to get a grip on if the bolt head shears off again, plus if you strip the threads in the dropout, e.g. when you fix the current issue, you can still make use of an unthreaded hole without needing to drill and tap for a larger size (which might weaken the dropout).

EDIT: reohn2 got there before me for most of this

[531colin]

Second thought...if this is steel/alloy corrosion, will the same chemical trick work as works with alloy seatpost corroded in steel frame, ie. soak it in Household Ammonia solution to dissolve the white oxide stuff???

[531colin]

Why will the reduced centre diameter of a centre drill wander less than eg a 2mm bit?
Or is it simply stiffer so you can bully it a bit?

[531colin]

If you have to drill it out and use M6, there can still be room for the cassette....http://www.westfieldfasteners.co.uk/A2_ScrewBolt_SHBtnFlg_M6.html

[byegad]

And grease the new bolt before you fit it. Next time it should come out!